Adds a way to specify traits in the jobs special area.
Hashset so you can specify multiple traits. Tested on Nuclear14 to give
the tribals a specific language in a friendly way.
```
special:
- !type:AddTraitSpecial
traits: [ LanguageTribal, LanguageChinese ]
```
(cherry picked from commit bc0708ab3f602f5f348f2e0a0585effac9f5c3e8)
